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Beginning with the successful contract bid on 5 June 1946, the B-52
went through several design steps; from a straight wing aircraft
powered by six turboprop engines to the
final prototype YB-52, with eight turbojet
engines. The aircraft made its first flight on 15 April 1952 with
"Tex" Johnston as pilot.

Built to carry nuclear weapons for Cold
War-era deterrence missions, the
B-52 Stratofortress replaced the Convair
B-36. Although a veteran of a number of wars, the
Stratofortress has dropped only conventional munitions in actual
combat. The B-52 carries up to of weapons.

The USAF has possessed B-52s in active service since 1955,
initially with the Strategic Air
Command (SAC), with all aircraft later absorbed into the
Air Combat Command (ACC)
following SAC's disestablishment in 1992. Superior performance at
high subsonic speeds and relatively low operating costs have kept
the B-52 in service despite more developed aircraft or modern
aircraft in service including the Mach 3 XB-70 Valkyrie, the supersonic B-1B Lancer, and the B-2
Spirit. In January 2005, the B-52 became the second aircraft,
after the English Electric
Canberra, to mark 50 years of continuous service with its
original primary operator. There are six aircraft altogether that
have made this list as of 2009; the other four being the Tupolev Tu-95, the C-130 Hercules, the KC-135 Stratotanker, and the Lockheed U-2.

Development

Models 462 (1946) to 464-35
(1948)

Models 464-49 (1949) to B-52A
(1952)

On 23 November 1945, Air
Materiel Command (AMC) issued desired performance
characteristics for a new strategic bomber "capable of carrying out
the strategic mission without dependence upon advanced and
intermediate bases controlled by other countries". The aircraft was
to have a crew of five plus turret gunners, and a six-man relief
crew. It was required to cruise at 300 mph (240 kn,
480 km/h) at 34,000 feet (10,400 m) with a combat
radius of 5,000 miles (4,300 nmi, 8,000 km). The armament was to
consist of an unspecified number of 20 mm cannon and
10,000 pounds (4,500 kg) of
bombs. On 13 February 1946, the Air Force issued bid invitations
for these specifications, with Boeing, Consolidated Aircraft, and Glenn L.Martin Company submitting
proposals.

On 5 June 1946, Boeing's Model 462, a straight-wing aircraft
powered by six Wright T35turboprops with a gross weight of
360,000 pounds (160,000 kg) and combat radius of
3,110 miles (2,700 nmi, 5,010 km), was declared the
winner. On 28 June 1946, Boeing was issued a letter of contract for
US$1.7 million (1946 dollars) to build a full-scale mock-up of the new XB-52 and do preliminary
engineering and testing. However, by October 1946, the Air Force
began to express concern about the sheer size of the new aircraft
and its inability to meet the specified design requirements. In
response, Boeing produced Model 464, a smaller four-engine version
with a 230,000 pound (105,000 kg) gross weight, which was
briefly deemed acceptable.

Then, in November 1946, the Deputy Chief of Air Staff for Research
and Development, General Curtis LeMay,
expressed the desire for a cruise speed of 400 miles per hour
(345 kn, 645 km/h), to which Boeing responded with a
300,000 pound (140,000 kg) aircraft. In December 1946,
Boeing was asked to change their design to a four-engine bomber
with a top speed of 400 miles per hour, range of
12,000 miles (10,000 nmi, 19,000 km), and the
ability to carry a nuclear weapon.
The aircraft could weigh up to 480,000 pounds
(220,000 kg). Boeing responded with two models powered by the
T-35 turboprops. The Model 464-16 was a "nuclear-only" bomber with
a 10,000 pound (4,500 kg) payload, while the Model 464-17
was a general purpose bomber with a 90,000 pound
(40,000 kg) payload. Due to the cost associated with
purchasing two specialized aircraft, the Air Force selected Model
464-17 with the understanding that it could be adapted for nuclear
strikes.

In June 1947, the military requirements were updated and the Model
464-17 met all of them except for the range. It was becoming
obvious to the Air Force that, even with the updated performance,
the XB-52 would be obsolete by the time it entered production and
would offer little improvement over the Convair B-36. As a result, the entire project
was put on hold for six months. During this time, Boeing continued
to perfect the design which resulted in the Model 464-29 with a top
speed of 455 miles per hour (395 kn, 730 km/h) and a
5,000-mile range. In September 1947, the Heavy Bombardment
Committee was convened to ascertain performance requirements for a
nuclear bomber. Formalized on 8 December 1947, these called for a
top speed of 500 miles per hour (440 kn, 800 km/h)
and an 8,000 mile (7,000 nmi, 13,000 km) range, far
beyond the capabilities of 464-29.

The outright cancellation of the Boeing contract on 11 December
1947 was staved off by a plea from its president William McPherson Allen, and in
January 1948 Boeing was instructed to thoroughly explore recent
technological innovations, including aerial refueling and the flying wing. Noting stability and control
problems Northrop was
experiencing with their YB-35 and
YB-49 flying wing bombers, Boeing
insisted on a conventional aircraft, and in April 1948 presented a
US$30 million (1948 dollars) proposal for design,
construction, and testing of two Model 464-35 prototypes. Further
revisions of specifications during 1948 resulted in an aircraft
with a top speed of 513 miles per hour (445 kn,
825 km/h) at 35,000 feet (10,700 m), a range of
6,909 miles (6,005 nmi, 11,125 km), and a
280,000 pounds (125,000 kg) gross weight which included
10,000 pounds (4500 kg) of bombs and
19,875 US gallons (75,225 L) of fuel.

Pre-production

In May 1948 AMC asked Boeing to incorporate the previously
discarded, but now more fuel-efficient, jet engine into the design.
This resulted in Boeing developing yet another revision — in
July 1948, Model 464-40 substituted Westinghouse J40turbojets for the turboprops. Nevertheless, on 21
October 1948, Boeing was told to create an entirely new aircraft
using Pratt & Whitney
J57 turbojets.

On 25 October, Boeing engineers produced a proposal and a
hand-carved model of 464-49. The new design built upon the basic
layout of the B-47 Stratojet with 35°
swept wings, eight engines paired in four
underwing pods, and bicycle landing gear with wingtip outrigger
wheels. A notable feature of the landing gear was the ability to
pivot the main landing gear up to 20° from the aircraft centerline
to increase safety during crosswind
landings. The aircraft was projected to exceed all design
specifications. Although the full-size mock-up inspection in April
1949 was generally favorable, range again became a concern since
the J40s and the early model J57s had excessive fuel
consumption.

Despite talk of another revision of specifications or even a full
design competition among aircraft manufacturers, General LeMay, now
in charge of Strategic Air Command, insisted that performance
should not be compromised due to delays in engine development. In a
final attempt to increase the range, Boeing created the larger
464-67, stating that once in production, the range could be further
increased in subsequent modifications. Following several direct
interventions by LeMay, on 14 February 1951 Boeing was awarded a
production contract for 13 B-52As and 17 detachable reconnaissance
pods. The last major design change, also at the insistence of
General LeMay, was a switch from the B-47 style tandem seating to a
more conventional side-by-side cockpit which increased the
effectiveness of the copilot and reduced crew fatigue. Both XB-52
prototypes featured the original tandem seating arrangement with a
framed bubble-type canopy.

The YB-52,
the second XB-52 modified with more operational equipment) first
flew on 15 April 1952, a 2 hour 21 minute flight from Renton
Field in Renton, Washington to Larson
AFB with Boeing test pilot Alvin M.Johnston and Air Force Lieutenant Colonel
Guy M.Townsend. The XB-52 followed on 2 October
1952. The thorough development, including 670 days in the wind tunnel and 130 days of aerodynamic and
aeroelastic testing, paid off with smooth flight testing.
Encouraged, the Air Force increased its order to 282 B-52s.

First production

Only three of the 13 B-52As ordered were built. All were returned
to Boeing, and used in their test program. On 9 June 1952 the
February 1951 contract was updated to order the aircraft under new
specifications. The final 10, the first aircraft to enter active
service, were completed as B-52Bs. At the roll out ceremony on 18
March 1954, Air Force Chief of Staff, General Twining said:

Design

Upgrades and modifications

In November 1959, SAC initiated the Big Four modification
program (also known as Modification 1000) for all
operational B-52s except early B models. The program was completed
by 1963. The four modifications were:

Ability to perform all-weather, low-altitude
(below 500 feet or 150 m) interdiction as a response to
advancements in Soviet
Union's missile defenses. The low-altitude flights
were estimated to accelerate structural fatigue by at least a
factor of eight, requiring costly repairs to extend service
life.

The ability to carry up to 20 AGM-69
SRAM nuclear missiles was added to G and H models starting in
1971.Fuel leaks due to deteriorating Marman
clamps continued to plague all variants of the B-52. To this
end, the aircraft were subjected to Blue Band (1957),
Hard Shell (1958), and finally QuickClip (1958)
programs. The latter fitted safety straps which prevented
catastrophic loss of fuel in case of clamp failure.

Ongoing problems with advanced avionics were addressed in the
Jolly Well program, completed in 1964, which improved
components of the AN/ASQ-38 bombing navigational computer and the
terrain computer. The MADREC (Malfunction Detection and Recording)
upgrade fitted to most aircraft by 1965 could detect failures in
avionics and weapons computer systems, and was essential in
monitoring the Hound Dog missiles. The electronic countermeasures
capability of the B-52 was expanded with Rivet Rambler
(1971) and Rivet Ace (1973).

In order to improve the ability to operate safely at low level
during both day and night, the AN/ASQ-151 Electro-Optical Viewing
System (EVS), consisting of a Low Light Level Television
(LLLTV) and a Forward Looking
Infra-Red (FLIR) system mounted in blisters under the noses of
B-52Gs and Hs between 1972 and 1976. In order to further improve
the B-52s offensive ability, it was decided to fit Air Launched
Cruise Missiles (ALCMs). After testing of both the Air-Force backed
Boeing AGM-86 and the Navy backed
General Dynamics AGM-109 Tomahawk,
the AGM-86B was selected for operation by the B-52 (and ultimately
by the B-1 Lancer). A total of 194 B-52Gs and Hs were modified to
carry AGM-86s, carrying 12 missiles on underwing pylons, with 82
B-52Hs further modified to carry another eight missiles on a rotary
launcher fitted in the aircraft's bomb-bay. In order to conform
with the requirements of the SALT II Treaty for cruise
missile capable aircraft to be readily identified by reconnaissance
satellites, the cruise missile armed B-52Gs were modified with a
distinctive wing root fairing. As all B-52Hs were assumed to be
modified, no visual modification of these aircraft was required. In
1990, the stealthy AGM-129 ACM cruise
missile entered service. Although originally intended to replace
the AGM-86 its high cost and the end of the Cold War stopped
production after only 450 were made. Unlike the AGM-86, no
conventional (i.e. non-nuclear) armed version was built.

Structural fatigue, exacerbated
by the change to low-altitude missions, was first dealt with in the
early 1960s by the three-phase High Stress program which
enrolled aircraft at 2,000 flying hours. This was followed by a
2,000-hour service life extension to select airframes in 1966-1968,
and the extensive Pacer Plank reskinning completed in
1977. The wet wing introduced on G and H
models was even more susceptible to fatigue due to experiencing 60%
more stress during flight than the old wing. The wings were
modified by 1964 under ECP 1050. This was followed by a
fuselage skin and longeron replacement
(ECP 1185) in 1966, and B-52 Stability Augmentation
and Flight Control program (ECP 1195) in 1967.

Boeing has suggested re-engining the B-52H fleet with the Rolls-Royce RB211 534E-4. This would
involve replacing the eight Pratt & Whitney TF33s (total
thrust 8 × 17,000 lb) with four RB211s (total thrust 4 ×
37,400 lb). The RR engines will increase the range and payload
of the fleet and reduce fuel consumption. However, the cost of the
project would be significant. Procurement would cost approximately
US$2.56 billion (US$36 million × 71 aircraft). A Government Accountability
Office study of the proposal concluded that Boeing's estimated
savings of US$4.7 billion would not be realized and found that
it would cost US$1.3 billion over keeping the existing
engines. The higher cost was blamed on significant up-front
procurement expenditure, necessary re-tooling, and the RB211's
higher maintenance cost. The GAO report was subsequently disputed
in a Defense Sciences Board report in 2003 and revised in 2004 that
identified numerous errors in the prior evaluation of the Boeing
proposal, and urged the Air Force to re-engine the aircraft without
delay. Further, the DSB report stated the program would save
substantial funds, reduce greenhouse gas emissions, and increase
aircraft range and endurance, duplicating the results of a
Congressionally funded US$3M program office study conducted in
2003. However, the re-engining has not been approved as of
2009.

Lower deck of the B-52 dubbed the
battle station.

In 2007 the LITENING targeting
pod was fitted and commissioned increasing the combat
effectiveness of the aircraft during day, night and
under-the-weather conditions in the attack of ground targets with a
variety of standoff weapons under the guidance of lasers and the help of high resolution forward-looking
infrared sensor (FLIR) for visual display in
the infrared portion of the electromagnetic spectrum and charged coupled device (CCD-TV)
camera used to obtain target imagery in the visible portion, this
technology could also be used in real-time transmission to ground
communications networks and government agencies to gather
battlefield intelligence, assess battlefield damage, assess
terrorist activities and counter drug activity, further advancing
the B-52H's capabilities and uses.

Fuel research platform

In September 2006, the B-52 became one of the first US military
aircraft to fly using 'alternative' fuel. Syntroleum Corporation, a leader in Fischer-Tropsch process (FT)
technology, announced that its Ultra-Clean jet fuel was
successfully tested in a B-52. It took off from Edwards Air
Force Base with a 50/50 blend of FT and traditional JP-8 jet fuel which was burned in two of the eight
engines on the aircraft. This marked the first time that FT
jet fuel was tested in a military flight demo, and is the first of
several planned test flights.

On 15 December 2006, tail number 61-0034, Wise Guy took
off from Edwards with the synthetic fuel blend powering all eight
engines, the first time an Air Force aircraft was completely
powered by the mixture. The test flight was captained by Major
General Curtis Bedke, commander of the Edwards Flight Test Center,
the first time in 36 years that the installation's commander
performed a first flight in a flight test program. The flight
lasted seven hours, reached an altitude of 48,000 feet, and
was considered a success.

On 8 August 2007, Air Force SecretaryMichael Wynne certified the B-52H as
fully approved to use the FT blend, marking the formal conclusion
of the test program.

This
program is part of the Department of
Defense Assured Fuel Initiative, an effort to develop
secure domestic sources for the military energy needs. The
Pentagon hopes to reduce its use of crude oil from foreign
producers and obtain about half of its aviation fuel from
alternative sources by 2016. With the B-52 now approved to use the
FT blend, the USAF will use the test protocols developed during the
program to certify the C-17
Globemaster III and then the B-1B to
use the fuel (the first B-1 test flight took place in March, 2008).
The Air Force intends to test and certify every airframe in its
inventory to use the fuel by 2011.

Operational history

Although the B-52A was the first production variant, these aircraft
were used only in testing. The first operational version was the
B-52B which was developed in parallel with the prototypes since
1951. First flying in December 1954, B-52B, AF
Serial Number 52-8711, entered operational service with 93rd Heavy Bombardment Wing at
Castle Air Force
Base, California, on 29 June 1955. The wing became
operational on 12 March 1956. The training for B-52 crews consisted
of five weeks of ground school and four weeks of flying,
accumulating 35–50 hours in the air. The new B-52Bs replaced
operational B-36s on a one-to-one basis.

Early operations were complicated by lack of spares and ground
facilities while ramps and taxiways deteriorated under the weight
of the aircraft. The fuel system was prone to leaks and icing, and
bombing and fire control computers were unreliable. The two-story
cockpit presented a unique climate control problem – the pilots'
cockpit was heated by sunlight while the observer and the navigator
on the bottom deck sat on the ice cold floor. Thus, comfortable
temperature setting for the pilots caused the other crew members to
freeze, while comfortable temperature for the bottom crew caused
the pilots to overheat. The J57 engines were still new and
unreliable. Alternator failure caused the
first fatal B-52 crash in February 1956, which resulted in a brief
grounding of the fleet. In July, fuel and hydraulic system problems
again grounded the B-52s. To avoid maintenance problems, the Air
Force set up Sky Speed teams of 50 maintenance contractors
at each B-52 base. In addition to maintenance, the teams performed
routine checkups which took one week per aircraft.

On 21 May
1956, a B-52B (52-0013) dropped its first live hydrogen bomb (a Mk-15) over the Bikini Atoll. On 24–25 November 1956, four B-52Bs of the
93rd BW and four B-52Cs of the 42nd BW flew nonstop around the
perimeter of North America in Operation Quick Kick,
covering 15,530 miles (13,500 nm, 25,000 km) in 31
hours 30 minutes. SAC noted that the flight time could have been
reduced by 5–6 hours if the four inflight refuellings were done by
fast jet-powered tanker aircraft rather than propeller-driven
KC-97 Stratotankers. In a
demonstration of the B-52s global reach, on 16–18 January 1957,
three B-52Bs made a nonstop flight around the world during
Operation Power
Flite, covering 24,325 miles (21,145 nm,
39,165 km) in 45 hours 19 minutes (536.8 smph) with several
in-flight refuelings by KC-97s. The 93rd Bomb Wing received the
Mackay Trophy for their
accomplishment.

The B-52 set many records over the next few years. On 26 September
1958, a B-52D set a world speed record of 560.705 miles per
hour (487 kn, 902 km/h) over a 10,000 kilometers
(5,400 nm, 6,210 mi) closed circuit without a payload.
The same day, another B-52D established a world speed record of
597.675 miles per hour (519 kn, 962 km/h) over a
5,000 kilometer (2,700 nmi, 3,105 mi) closed circuit
without a payload. On 14 December 1960, a B-52G set a world record
by flying unrefueled for 10,078.84 miles (8,762 nm,
16,227 km). The flight lasted 19 hours 44 minutes (510.75
smph). On
10–11 January 1962, a B-52H set a world record by flying
unrefuelled from Kadena Air
Base, Okinawa, Japan, to
Torrejon Air
Base, Spain, covering 12,532.28 miles
(10,895 nmi, 20,177 km).

During this time, at the Strategic Air Command's peak strength in
1963, 650 B-52s were in operation in 42 squadrons at 38 air
bases.

In informal circumstances, the official name
Stratofortress is rarely used; personnel involved with the
aircraft most commonly referred to it as BUFF (Big Ugly
Fat Fucker).

Vietnam War

With the escalating situation in Southeast Asia, in June 1964 28
B-52Fs were fitted with external racks for 24× 750 pound
(340 kg) bombs under project South Bay. An additional
46 aircraft received similar modifications under project Sun
Bath. In March 1965, the United States commenced Operation Rolling Thunder, and the
first combat mission of Operation
Arc Light was flown by B-52Fs on 18 June 1965, when 30 bombers
of the 9th and 441st Bombardment Squadrons struck a communist
stronghold near Ben Cat in South Vietnam. The first wave of bombers
arrived too early at a designated rendezvous point, and while
maneuvering to maintain station, two B-52s collided, resulting in
the loss of both bombers and eight crewmen. The remaining bombers,
minus one more which turned back due to mechanical problems,
continued on towards the target, which was bombed
successfully.

B-52F releasing its payload of bombs
over Vietnam.

In December 1965, a number of B-52Ds underwent Big Belly
modifications to increase bomb capacity for carpet bombings. While the external payload
remained at 24× 500 pound (227 kg) or 750 pound
(340 kg) bombs, the internal capacity increased from 27 to 84×
500 pound bombs or from 27 to 42× 750 pound bombs. The
Big Belly modification now created enough capacity for a total of
60,000 pounds (27,215 kg) in 108 bombs. Thus modified,
B-52Ds could carry 22,000 pounds (9,980 kg) more than
B-52Fs. Replacing B-52Fs, modified B-52Ds entered
combat in April 1966 flying from Andersen Air Force Base, Guam. Each
bombing mission lasted ten to 12 hours with an aerial refueling by KC-135 Stratotankers. In spring 1967, the
aircraft began flying from U Tapao Airfield in Thailand giving the aircraft the advantage of not requiring
in-flight refueling. These missions lasted only 2 to 3
hours. On
15 April 1968, a Replacement Training Unit was established at
Castle
AFB which converted B-52E through B-52H crews to B-52Ds
so they could participate in combat in Southeast Asia.

On 22 November 1972, a B-52D (55-0110) from U-Tapao was hit by a
SAM while on a raid over
Vinh. The crew was forced to abandon the damaged aircraft over
Thailand. This was the first B-52 to be destroyed by hostile fire
in Vietnam.

The zenith of B-52 attacks in Vietnam was Operation Linebacker II
(sometimes referred to as the Christmas Bombing) which consisted of
waves of B-52s (mostly D models, but some Gs without jamming
equipment and with a smaller bomb load). Over 12 days B-52s
flew 729 sorties, dropping 15,237 tons of bombs on Hanoi, Haiphong, and other targets. In total, 30 B-52s were
lost during the war, including ten B-52s being shot down over North
Vietnam with five others being damaged and crashing in Laos or
Thailand.

Air-to-air victories

During the Vietnam War, B-52D tail gunners were credited with shooting down
two MiG-21 "Fishbeds". The
B-52's first aerial MiG kill occurred
on 18 December 1972, when tail gunner SSgt Samuel O. Turner, locked onto an
intercepting North Vietnamese Air Force MiG-21 during Operation Linebacker II. Turner's
Stratofortress just completed its
bomb run and was heading outbound when the enemy interceptor closed
in on his bomber. Both the MiG and the B-52
locked onto one another, and when the interceptor was within range,
Turner fired a burst of quad.50 caliber machine gun fire into
the enemy plane causing a gigantic explosion aft of Turner's
bomber. The aerial victory was witnessed by MSG Lewis E. Le Blance
flying tail gunner in a nearby Stratofortress. Turner's B-52, tail
number 55-0676, is currently preserved and on display at Fairchild AFB in Spokane, Washington.

On 24 December 1972, during the same bombing campaign, A1C Albert E. Moore, flying tail gunner
in the B-52 Diamond Lil, acquired a fast approaching
target as his bomber was headed to bomb the Thai Nguyen railroad yards. Maintaining target acquisition on
the interceptor, Moore opened fire with his quad fifties at 4,000 yards, maintaining fire until the
enemy aircraft disappeared from his scope. Moore's aerial victory
was observed by TSG Clarence W. Chute, a tail gunner aboard another
Stratofortress, who observed the MiG-21 to catch fire and fall away.
The
Diamond Lil is currently preserved and on display at the
United States Air Force
Academy in Colorado. SSG Turner was awarded a Silver Star for his actions and Airman Moore has
the distinction of being the last bomber
gunner to shoot down an enemy aircraft with machine guns in aerial
combat during war time. The last Arc Light mission took place
on 15 August 1973 and all B-52s left Southeast Asia shortly
after.

The downing of these MiG-21s makes the B-52 the largest aircraft to
be credited with an air-to-air "kill" in combat.

Cold War

During the Cold War, B-52s performed
airborne alert duty under code names such as Head Start,
Chrome Dome, Hard
Head, Round Robin, and Giant Lance.
Bombers
loitered near points outside the Soviet Union to provide rapid first strike or retaliation
capability in case of nuclear war.

A few time-expired E models were retired in 1967 and 1968, but the
bulk (82) were retired between May 1969 and March 1970. Most F
models were also retired between 1967 and 1973, but 23 survived as
trainers until late 1978.

The fleet of D models served much longer. Eighty D models were
updated under the Pacer Plank program (ECP 1581) at
Boeing's Wichita plant. Skinning on the lower wing and fuselage was
replaced, and various structural components were renewed. Work was
completed in 1977. The fleet of D models stayed largely intact
until late 1978, when 37 un-upgraded Ds were retired. The remainder
were retired between 1982 and 1983.

The remaining G and H models were used for nuclear standby
("alert") duty as part of the United States' nuclear triad. This triad was the combination
of nuclear-armed land-based missiles, submarine-based missiles and
manned bombers. The B-1B Lancer which was
intended to supplant the B-52, replaced only the older models and
the supersonic FB-111.

After the fall of the Soviet Union, the B-52Gs were destroyed per
the terms of the Strategic Arms Reduction
Treaty (START). AMARG was tasked
with eliminating 365 B-52 bombers. The progress of this task
was to be verified by Russia via satellite and first-person
inspection at the AMARG facility. Initially, the B-52s were chopped
into pieces with a 13,000 pound guillotine.

In 1991, B-52s ceased continuous 24-hour SAC alert duty.

Gulf War and later

On 16
February 1991, a flight of B-52Gs launching from and returning to
Barksdale
AFB, Louisiana, struck targets inside Iraq. This
was at the time the longest distance combat mission in history: 35
hours and 14,000 miles round trip. Over the next months,
B-52Gs operating from bases at Jeddah, Saudi Arabia, RAF Fairford
in the United Kingdom, Moron AB, Spain and on the island of
Diego
Garcia flew low level bombing missions. The B-52s
moved to high level missions after the first three nights.
Coalition forces ensured air superiority and were able to suppress
air defense systems capable of reaching bombers at a higher
altitude. B-52s were an important part of the air war during
Operation Desert Storm as
they could be employed with impunity. The conventional strikes were
carried out by three bombers dropping up to 153 750 pound
bombs at a time, covering an area one and a half miles long by one
mile wide. The bombings demoralized the defending Iraqi troops, and
they could be induced to surrender rather than be destroyed. Flying
approximately 1620 sorties in the Gulf War, B-52s delivered 40% of
the weapons dropped by coalition forces, while suffering only one
non-combat aircraft loss, with several receiving minor damage from
enemy action.

On 2–3
September 1996, two B-52H struck Baghdad power stations and
communications facilities with 13 AGM-86C air-launched cruise
missiles (ALCM) as part of Operation Desert Strike, a
34-hour, 16,000 mile round trip mission from Andersen AFB, Guam—the longest
distance ever flown for a combat mission. Only two days
prior, the crews completed 17-hour flights from Louisiana to
Guam.

Stratofortress video
in-action.

Since the mid-1990s, the B-52H has been the only variant remaining
in military service; it is currently stationed at:

An additional B-52H is controlled by NASA as part of the
Heavy-lift Airborne Launch program.

The B-52 also contributed to Operation Enduring Freedom
in 2001 (Afghanistan/Southwest Asia), providing the ability to
loiter high above the battlefield
and provide Close Air Support (CAS) through the use of precision
guided munitions, a mission which previously would have been
restricted to fighter and ground attack aircraft.

B-52s also played a role in Operation Iraqi Freedom, which
commenced on 20 March 2003 (Iraq/Southwest Asia). On the night of
21 March 2003, B-52Hs launched at least one hundred AGM-86C CALCM.

In August 2007, a B-52H ferrying AGM-129
ACM cruise missiles from Minot Air Force Base to Barksdale Air
Force Base for dismantling was mistakenly
loaded with six missiles from which the nuclear warhead was not
removed. The weapons did not leave USAF custody and were secured at
Barksdale.

, 94 of the original 744 B-52 aircraft were still operational within the U.S. Air Force. Four of 18 B-52Hs from Barksdale AFB that are currently being retired are in the "boneyard" of 309th AMARG at Davis-Monthan AFB as of 8 September 2008.

Future of the B-52

Even while the Air Force works on new bombers scheduled for
2037 it intends to keep the B-52H in
service until at least 2040, nearly 80 years after production
ended. This is an unprecedented length of service for a military
aircraft. B-52s are periodically refurbished at the
USAF maintenance depots such as Tinker Air Force Base, Oklahoma.

The USAF continues to rely on the B-52 because it remains an
effective and economical heavy bomber, particularly in the type of
missions that have been conducted since the end of the Cold War
against nations that have limited air defense capabilities. The
B-52's capacity to "loiter" for
extended periods over (or even well outside) the battlefield, while
delivering precision standoff and
direct fire munitions, has been a
valuable asset in conflicts such as Operation Iraqi Freedom.

The speed of the B-1 Lancer and the
stealth of the B-2 Spirit have only been
useful until enemy air defenses were destroyed, a task that has
been swiftly achieved in recent conflicts. The B-52 boasts the
highest mission capable rate of the three types of heavy bombers
operated by the USAF. Whereas the B-1 averages a 53% ready rate,
and the B-2 achieved a 26%, the B-52 averages 80% as of 2001.

Additionally, a proposed variant of the B-52H was the EB-52. This
version would have modified and augmented 16 B-52H airframes with
additional electronic jamming capabilities. This new aircraft would
have given the USAF an airborne jamming capability that it has
lacked since retiring the EF-111 Raven.
The program was cancelled in 2005 following removal of funding for
the stand-off jammer. The program was revived in 2007 but funding
was again canceled in early 2009.

Variants

Production numbers

Variant

Produced

Entered Service

XB-52

2 (1 redesignated YB-52)

prototypes

B-52A

3

NB-52A

1 Modified B-52A

B-52B

50

29 June 1955

RB-52B

27 Modified B-52Bs

NB-52B

1 Modified B-52B

B-52C

35

June 1956

B-52D

170

December 1956

B-52E

100

December 1957

B-52F

89

June 1958

B-52G

193

13 February 1959

B-52H

102

9 May 1961

Grand total

744 production

The B-52 went through several design changes and variants over its
10 years of production.

B-52A

Only three of the first production
version, the B-52A, were built, all loaned to Boeing for flight
testing. The first production B-52A differed from prototypes in
having redesigned forward fuselage. The bubble canopy and tandem
seating was replaced by a side-by-side arrangement and a
21 inch (53 cm) nose extension accommodated more avionics and a new 6th crew member. In the rear
fuselage a tail turret with four 0.50 inch (12.7 mm)
machine guns with a fire-control system, and a water injection system to augment
engine power with a 360 US gallon (1,363 L) water
tank was added. The aircraft also carried a
1,000 US gallon (3,785 L) external fuel tank under
each wing. The tanks acted as dampeners to reduce wing flex and
also kept wingtips close to the ground for ease of
maintenance.

NB-52A carrying an X-15

NB-52A

The last B-52A (serial 52-0003) was
modified and redesignated NB-52A in 1959 to carry the North American X-15. A pylon was fitted
under the right wing between the fuselage and the inboard engines
with a 6 feet x 8 feet (1.8 m x 2.4 m) section
removed from the right wing flap to
fit the X-15 tail. Liquid oxygen and hydrogen peroxide tanks were
installed in the bomb bays to fuel the X-15 before launch. First
flight with X-15 was on 19 March 1959, with the first launch on 8
June 1959. The NB-52A, named "The High and Mighty One" carried the
X-15 on 93 of the program's 199 flights.

B-52B/RB-52B

The B-52B was the
first version to enter service with the USAF on 29 June 1955, with
the 93rd Bombardment Wing at
Castle
AFB in California. This version included minor
changes to engines and avionics in the attempt to fix minor
problems. Temporary grounding of the aircraft after a crash in
February 1956 and again the following July caused training delays,
and at mid-year there were still no combat-ready B-52 crews.

Of the 50 B-52Bs built, 27 were capable of carrying a
reconnaissance pod as RB-52Bs (the crew was increased to eight in
these aircraft). The 300 pound (136 kg) pod contained
radio receivers, a combination of K-36, K-38, and T-11 cameras, and
two operators on downward-firing ejection
seats. The pod required only four hours to install.

Seven B-52Bs were brought to B-52C standard under Project
Sunflower.

NB-52B

The NB-52B was B-52B number 52-0008
converted to an X-15 launch platform. It subsequently flew
as the "Balls
8" in support of NASA research
until 17 December 2004, making it the oldest flying B-52B.
It was replaced by a modified B-52H.

B-52C

In the B-52C the fuel capacity (and
range) was increased to 41,700 US gallons by adding
larger 3000 US gallon underwing fuel tanks. The gross
weight was increased by 30,000 pounds (13,605 kg) to
450,000 pounds. The belly of the aircraft was painted with
antiflash white paint, which was
intended to reflect thermal radiation away after a nuclear
detonation.

RB-52C

The RB-52C was the designation given,
but seldom used, to B-52Cs converted for reconnaissance duties in a
similar manner to RB-52Bs.

B-52D

The B-52D was a dedicated long-range
bomber without a reconnaissance option. The Big Belly
modifications allowed the B-52D to carry heavy loads of
conventional bombs for carpet bombing
over Vietnam. Aircraft assigned to Vietnam were painted camouflage
with black bellies to defeat searchlights.

B-52E

In the B-52E the aircraft received an
updated avionics and bombing navigational system, which was
eventually debugged and included on following models.

One E aircraft (AF Serial No. 56-0631) modified as a
testbed for various B-52 systems. Redesignated NB-52E, the aircraft
was fitted with canards and a
Load Alleviation and Mode Stabilization system (LAMS) which reduced
airframe fatigue from wind gusts during low level flight. In one
test, the aircraft flew 10 knots (11.5 mph,
18.5 km/h) faster than the never exceed
speed without damage because the canards eliminated 30% of
vertical and 50% of horizontal vibrations caused by wind
gusts.

B-52F: In the B-52F, the aircraft was
given J57-P-43W engines with a larger capacity water injection
system and new alternators. This model had problems with fuel
leaks, but were eventually solved by several service modifications:
Blue Band, Hard Shell, and
QuickClip.

B-52G

The B-52G was proposed to extend the
B-52's service life during delays in the B-58 Hustler program. At first, a radical
redesign was envisioned with a completely new wing and Pratt & Whitney J75 engines.
This was rejected to avoid slowdowns in production, although
changes were implemented. The most significant of these was the
brand new "wet" wing with integral fuel tanks which considerably
increased the fuel capacity — gross aircraft weight went up by
38,000 pounds (17,235 kg) compared with prior variants.
In addition, a pair of 700 US gallon (2,650 L)
external fuel tanks was fitted under the wings. In this model, the
traditional ailerons were eliminated,
instead utilizing spoilers for
roll control. The tail fin was shortened by 8 feet
(2.4 m), water injection system capacity was increased to
1,200 US gallons (4,540 L), and the nose radome was
enlarged. The tail gunner was provided with an ejection seat and
moved to the main cockpit. Dubbed the "Battle Station" concept, the
offensive crew (pilot and copilot on the upper deck and the two
bombing navigation system operators on the lower deck) faced
forward, while the defensive crew (tail gunner and ECM operator) on
the upper deck faced aft. The B-52G entered service 13 February
1959 (a day earlier, the last B-36 was retired, making SAC an
all-jet bomber force). Nearly all B-52Gs were destroyed in
compliance with the Strategic Arms Reduction
Treaty of 1992. A few examples remain in museums and as
static displays at various air force bases.

B-52H

The B-52H had the same crew and
structural changes as the B-52G. The most significant upgrade was
the switch to TF33-P-3turbofan engines which, despite the initial
reliability problems (corrected by 1964 under the Hot Fan
program), offered considerably better performance and fuel economy
than the J57 turbojets. The ECM and
avionics were updated, a new fire control system was fitted, and
the rear defensive armament was changed from machine guns to a
20 mm M61 Vulcan cannon (later
removed in 1991-94). A provision was made for four AGM-48 Skyboltballistic missiles. First flight 10 July
1960, entered service 9 May 1961. This is the only variant still
operational. A total of 744 B-52s were built. The last production
aircraft, B-52H AF Serial No. 61-0040, left the factory on 26
October 1962.

On 13 January 1964, a B-52D carrying two nuclear bombs suffered
a structural failure in flight that caused the tail section to
shear off. Four crew ejected successfully before the
aircraft crashed near Cumberland, Maryland. Two crew subsequently perished on the
ground because of hypothermia, while
another who was unable to eject died in the aircraft; both weapons
were recoverd.

On 17
January 1966, a fatal collision occurred between a B-52G and a KC-135 Stratotanker over Palomares, Spain. The two unexploded B-28 FI 1.45-megaton-range nuclear bombs on
the B-52 were eventually recovered; the conventional explosives of
two more bombs detonated on impact, with serious dispersion of both
plutonium and uranium, but without triggering a nuclear explosion.
After the crash, of contaminated soil was sent to the United
States. In 2006, an agreement was made between the U.S. and Spain
to investigate and clean the pollution still remaining as a result
of the accident.

On 21
January 1968, a B-52G, with four nuclear bombs aboard as part of
Operation Chrome Dome,
crashed
on the ice of the North Star Bay while attempting an emergency landing at Thule Air
Base, Greenland. The resulting fire caused extensive
radioactive contamination, the cleanup of which lasted until
September of that year. Following closely on the Palomares
incident, the clean-up costs and political consequences proved too
high to risk again, so SAC ended the airborne alert program the
following day.

On 31 March 1972, a B-52D, AF Serial No. 56-0625, departed
McCoy Air
Force Base, Florida on a routine training mission.
Assigned to the 306th Bombardment
Wing, the unarmed aircraft sustained multiple engine failures
and engine fires on engines #7 and #8 shortly after takeoff.
The
aircraft immediately attempted to return to the base, but crashed
just short of Runway 18R in a residential area of Orlando,
Florida, approximately 1 mile north of McCoy AFB, destroying or damaging eight homes. The
flight crew of 7 airmen and 1 civilian on the ground were
killed.

On October 16, 1984, a B-52 slammed into Hunts Mesa in Monument
Valley, Arizona, sending a fireball high into the air, killing two
and injuring five.

Ground tests and checkouts carried out on 29 November 1951
resulted in the XB-52's pneumatic system's failure during a
full-pressure test with the resulting explosion severely damaging
the wing trailing edge. The prototype was returned to the
production hall for repairs.

The following military aircraft are the only aircraft larger
than the B-52 in some manner (parameter listed in parenthesis may
not be the only figure that exceeds the corresponding parameter of
the B-52) and possess an air-to-air capability; none of them have
any combat kills: B-36 Peacemaker (wingspan), Convair YB-60 (wingspan),
Ilyushin
Il-76D (payload).